Gronseth Drywall Systems, Inc., is in discussions with its investment bankers regarding the issuance of new bonds. The investment banker has informed the firm that different maturities will carry different coupon rates and sell at different prices. The firm must choose among several alternatives. In each case, the bonds will have a $1,000 par value and flotation costs will be $30 per bond. The company is taxed at 40%. Use the approximation formula to calculate the after-tax cost of financing with the following alternative.

Coupon rate: 11%

Time to maturity: 20 years

Premium or discount: $220

The after-tax cost of financing using the approximation formula is _____%